The tremendous level of environmental stress and the rise in food demand have made it extremely difficult to ensure world food safety. In such scenarios, wild crop species serve as genetic reservoirs, enriching the yield, quality, and adaptability of modern cultivars. Domesticated or artificially selected varieties of crops are susceptible to various stresses like biotic and abiotic, which can be mitigated by the incorporation of desirable or novel alleles from wild species. Crop wild relatives (CWRs) include plant species that are nearer to crop species in the near evolutionary history as well as the immediate progenitor of crop species. However, employing CWRs directly for varietal development initiatives is usually not helpful due to the high frequencies of deleterious alleles in CWRs and the prevalence of crossover or chromosomal introgression barriers with domesticated species. Due to the increasing criticism of mitigation strategies like transgenics and the obvious threat posed by climate change, the importance of CWRs has increased. Systematic CWRs’ genetic diversity collection, conservation, and characterization are crucial in this era of genetic loss of diversity and species extinction. In this chapter, contribution of CWRs for crop improvement along with various difficulties and challenges associated with their utilization in breeding has been discussed.